The zona pellucida is a glycocalyx that surrounds the maturing mammalian oocyte. Using a murine follicle culture, we have demonstrated the biosynthesis of the zona in vitro and shown that its synthesis can be inhibited by FSH and LH. The zona pellucida is comprised of three major sulfate-containing glycoproteins which have been isolated by high performance liquid chromatography. As demonstrated on two-dimensional O'Farrell gels. each glycoprotein has marked charge and size heterogeneity which can be eliminated by pre-incubation with tunicamycin. We are now undertaking studies to determine the mechanisms of control of the expression of the genes coding for these three macromolecules as well as the role that the gene products play in the species-specific sperm binding.